1. Field of the Invention
The present invention relates to an optical pickup actuator, in which a pair of lenses, e.g., BD lens and DVD lens, are loaded on one pickup to record/reproduce information on/from optical discs having various write capacities such as BD (Blu-ray disc), CD, DVD and the like, by which drive and system configurations can be simplified, and by which the facilitation of the system configuration and high sensitivity of the actuator are provided since there exist no sensitivity deviations of tracking and focusing between BD and CD/DVD actuators.
2. Discussion of the Related Art
Currently, DVD (digital versatile disc) having a single-side recording capacity of 4.7 GB and 0.74 μm track pitch is on the market as an optical information storage disc of a large capacity. Yet, in case of writing about 135-minute HD (high definition) moving picture information on DVD, at least 23 GB recording capacity is needed.
In order to write such a large volume of data, a blue purple light source having a wavelength shorter than that of a previous red light source has been provided to develop the Blu-ray disc (hereinafter abbreviated BD) on which information can be recorded and reproduced using the blue purple light source.
Meanwhile, in order to raise a numerical aperture (NA) of an objective lens, a high-NA lens should be used.
Since BD uses a high-NA lens designed to have a focus fitted on a recording surface of 0.1 mm thickness, there exists compatibility problem in using the BD lens for another optical disc such as CD, DVD, or the like, which has a recording surface thickness different from that of BD.
Namely, spherical aberration (SA) generated from a distance variation between recording surfaces, coma aberration (CA) generated from a tilt of an optical disc (e.g., surface vibration, etc.), astigmatism (AS) by defocus, and the like bring about degradation of optical characteristics.
Moreover, the lens for CD or DVD is also needed in addition to the lens for BD for securing compatibility with various kinds of optical discs due to such a problem as the difference of optical power (write power) and the like.
For such reasons, a pair of optical pickups are loaded on one drive in a manner of configuring separately the DVD or CD optical pickup and the BD optical pickup.
However, the above-configured drive fails to avoid the increase of its overall configuration size as well as product cost.